Snow and ice control over primary, high speed highways such as interstate systems typically is carried out by governmental authorities with the use of dump trucks which are quite robust, for example, typically exceeding 28,000 pounds gross vehicle weight (GVW). This robust size requires operators with commercial drivers license qualifications. In general, the trucks are somewhat similar in general layout of the cab and the like from manufacturer to manufacturer in view of the anticipated primary highway related endeavors. These trucks are seasonally modified by the addition of snow-ice treatment components. Such components will include forwardly mounted plows, wing plows, scrapper plows and rearwardly-mounted mechanisms for broadcasting materials such as salt or brine containing salt. The classic configuration for the latter broadcasting mechanisms includes a feed auger extending along the back edge of the dump bed of the truck. This hydraulically driven auger effects a metered movement of material from the bed of the truck into a rotating spreader disk or “spinner” which functions to broadcast the salt across the pavement being treated. To maneuver the salt-based material into the auger, the dump bed of the truck typically has been progressively elevated as the truck moves along the highway to be treated. Thus, when into a given run, the dump bed will be elevated, dangerously raising the center of gravity of the truck under inclement driving conditions. Generally, the snow-ice control mechanisms mounted on these trucks perform in conjunction with a hydraulic circuit which, for example, will carry out all season functions such as hoisting a dump bed and the like. The hydraulic systems very often are controlled with electronics which are mounted within the truck cab and have electrical feeder lines extending to feedback sensors mounted about the frame of the truck. Many such sensors and feedback lines along with associated couplers are seasonally removed and even though of high quality, are prone to corrosive failure in view of the rigid environment the trucks are exposed to. As a consequence, their replacement often is on a yearly basis.
An initial improvement in the controlled deposition of salt materials and the like has been achieved through the utilization of microprocessor driven controls over the hydraulics employed with the modified dump trucks. See Kime, et al., U.S. Pat. No. Re. 33,835, entitled, “Hydraulic System for Use With Snow-Ice Removal Vehicles”, reissued Mar. 3, 1992. This Kime, et al. patent describes a microprocessor-driven hydraulic system for such trucks with a provision for digital hydraulic valving control which is responsive to the instantaneous speed of the truck. With the hydraulic system, improved controls over the extent of deposition of snow-ice materials is achieved. Of further importance, the binary form of digital valving removes a requirement for the vulnerable feedback lines and associated sensors. This patent is expressively incorporated herein by reference.
Investigations into techniques for controlling snow-ice pavement envelopment have recognized the importance of salt in the form of salt brine in breaking the bond between ice and the underlying pavement. Without a disruption of that bond, little improvement to highway traction will be achieved. For example, a plow merely will scrape off the snow and ice to the extent possible, only to leave a slippery coating which may be more dangerous to the motorist than the pre-plowed road conditions.
When salt has been simply broadcast over an ice laden pavement from a typical spinner, it will have failed to form a brine of sufficient salt concentration to break the ice-pavement bond. The result is usually an ice coated pavement, in turn, coated with a highly dilute brine solution developed by too little salt, which will have melted an insufficient amount of ice for traction purposes. This condition is encountered often where granular salt material contains a substantial amount of “fines”. Fines are very small salt particles typically generated in the course of transporting, stacking, and storing road maintenance salt in dome-shaped warehouses and the like.
Road snow-ice control studies have revealed that the activity of ice melting serving to break the noted ice-pavement bond is one of creating a salt-water brine of adequate concentration. In general, an adequate salt concentration using conventional dispersion methods requires the distribution of an unacceptable quantity of salt on the pavement. Some investigators have employed a saturated brine as the normal treatment modality by simply pouring it on the ice covered highway surface from a lateral nozzle containing spray bar mounted behind a truck. A result has been that the thus-deposited brine concentration essentially immediately dilutes to ineffectiveness at the ice surface.
Attempting to remove ice from pavement by dissolving the entire amount present over the entire expanse of pavement to be treated is considered not to be acceptable from an economical as well as environmental standpoint. For example, a one mile, 12 foot wide highway lane with a one-fourth inch thickness of ice over it should require approximately 4 tons of salt material to make a 10% brine solution and create bare pavement at 20° F. Technical considerations for developing a salt brine effective to achieve adequate control are described, for example, by D. W. Kaufman in “Sodium Chloride: The Production and Properties of Salt and Brine”, Monograph Series 145 (Amer. Chem. Soc., 1960).
The spreading of a combination of liquid salt brine and granular salt has been considered beneficial. In this regard, the granular salt may function to maintain a desired concentration of brine for attacking the ice-pavement bond and salt fines are more controlled by dissolution in the mix. The problem of excessive salt requirements remains, however, as well as difficulties in mixing a highly corrosive brine with particulate salt. Typically, nozzle injection of the brine is the procedure employed. However, attempts have been made to achieve the mix by resorting to the simple expedient of adding concentrated brine over the salt load in a dump bed. This approach is effective to an extent. However, as the brine passes through the granular salt material, it dissolves the granular salt such that the salt will not remain in solution and will re-crystallize causing bridging phenomena and the like inhibiting its movement into a distribution auger.
The techniques of deposition of salts in a properly distributed manner upon highway surfaces also has been the subject of investigation. Particularly where bare pavement initially is encountered, snow-ice material deployed with conventional equipment will remain on the highway surface at the time of deposition only where the depositing vehicles are traveling at dangerously slow speeds, for example, about 15 m.p.h. Above those slow speeds, the material essentially is lost to the roadside and that material located within the wheel tracks of traffic will be disbursed. Observation of materials attempted to be deposited at higher speeds shows the granular material bouncing forwardly, upwardly, and being broadcast over the pavement edges such that deposition at the higher speeds is ineffective as well as dangerous and potentially damaging to approaching vehicles. The latter damage sometimes is referred to as “collateral damage” or damage to coincident traffic. However, the broadcasting trucks themselves constitute a serious hazard when traveling, for example, at 15 m.p.h., on dry pavement, which simultaneously is accommodating vehicles traveling, for example, at 65 m.p.h. The danger so posed has been considered to preclude the highly desirable procedure of depositing the salt material on dry pavement just before the onslaught of snow-ice conditions.
Kime, et al. in U.S. Pat. No. 5,318,226 entitled “Deposition of Snow-Ice Treatment Material From a Vehicle With Controlled Scatter”, issued Jun. 7, 1994 (incorporated herein by reference) describes an effective technique and mechanism for controlling the scatter of the so-called granules at higher speed. With the method, the salt materials are propelled by an impeller from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle line of travel. The result is an effective suspension of the projected materials over the surface of pavement under conditions of substantially zero velocity with respect to or relative to the surface of deposition. Depending upon vehicle speed desired, material deposition may be provided in controlled widths ranging from narrow to wider bands.
A practical technique for generating a brine of sufficient concentration to break the ice-pavement bond is described in U.S. Pat. No. 5,988,535 entitled “Method and Apparatus for Depositing Snow-Ice Treatment Material on Pavement” by Kime, issued Nov. 23, 1999. With this technique, ejectors are employed to deposit a salt-brine mixture upon a highway as a relatively narrow, continuous and compact band of material. To achieve such narrow band material deposition at practical highway speeds of 40 m.p.h. or more, the salt-brine mixture is propelled from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle. Further, the material is downwardly directed at an acute angle with respect to the plane defined by the pavement. When the salt-brine narrow band is deposited at the superelevated side of a highway lane, the resultant concentrated brine from the band is observed to gravitationally migrate toward the opposite or downhill side of the treated lane to provide expanded ice clearance. The result is a highly effective snow-ice treatment procedure with efficient utilization of salt materials.
An improvement in the zero relative velocity broadcasting technique is described in U.S. Pat. No. 6,446,879 entitled “Method and Apparatus for Depositing Snow-Ice Treatment Material on Pavement” by Kime, issued Sep. 10, 2002, in which narrow band ejection of salt and brine is provided in a manner wherein it is encountered by the rear drive wheels of a dump truck.
Over the recent past, investigators have returned to the subject of pre-treating a bare or dry highway pavement before a weather event occurs otherwise generating ice/pavement bond conditions. Rather than attempting to deposit granular salt on a highway, brine is placed on the roadway in small, angularly downwardly directed streams spaced about eight to twelve inches apart and usually extending across a width of one driving lane. The total application rate usually is thirty to sixty gallons of salt brine per lane mile. Where clear weather permits, the resultant brine strips will dry leaving a tenaciously bonded strip of fine salt along the pavement somewhat emulating paint. With continued dry weather, these fine crystalline strips will remain on the pavement for several days or more except for some deterioration along vehicle wheel track regions. When snow conditions then commence, the resultant moisture will activate the strips to attack the very development of an ice/pavement bond condition. Rubber edged squeegee plows have been used to remove a resultant un-bonded slush from the pretreated highway.
Kime, in U.S. Pat. No. 7,108,196 entitled “Method and Apparatus for Depositing Snow-Ice Treatment Liquid on Pavement”, issued Sep. 19, 2006, describes a brine pre-treatment method and apparatus wherein three streamer nozzles are employed, two of which are mounted laterally outwardly from the sides of the application truck and one is positioned between the rear wheels of the truck. Utilizing a vehicle speed responsive and accurate pump drive in conjunction with the streamer nozzle structures, liquid brine may be deposited at target volume levels per unit pavement mile outside of traffic wheel track zones so as to remain undisturbed pending the development of a weather event reactivating the brine. The outward streamer nozzles are employed to deposit liquid brine at the superelevated or near the crown portion of a highway lane. By positioning the streamer nozzles quite close to the pavement surface and aligning their axes in substantially parallel relationship with the plane defined by the pavement, very little overspray or splash otherwise occasioned by truck induced wind turbulence is encountered and a very high deposition efficiency is achieved. With the system, brine is deposited at relatively high highway speeds with little or no hindrance to coincident traffic.
The excellent effectiveness and attendant environmental and economic advantages of brine pre-treatment programs is significant. In general, governmental highway organizations consider that an initial application upon highways under snow-ice conditions, for example, on interstate highways, will be about 600 pounds of granular salt per mile. A pre-treatment of liquid brine at about 60 gallons per mile will evoke the use of a corresponding amount of salt from between about 100 and 125 pounds. Of particular economic interest, because the brine can be deposited well before an impending weather event, trucks and drivers can be utilized during normal working hours. In compliment with these economies, improvements have been made in techniques employed for forming the brine solutions prior to loading on the depositing trucks. See in this regard U.S. Pat. No. 6,736,153 by Kime, entitled “Brining System, Method and Apparatus”, issued May 18, 2004.
While substantial technical advances have been witnessed by authorities responsible for snow-ice control over primary or interstate highways, municipal and township governments responsible for snow-ice treatment of secondary roads traditionally have employed smaller and more maneuverable trucks. Such trucks fall below the 28,000 pound GVW criteria. The trucks are seasonally retrofitted with forward plows, augers and spinners which for the slower speeds involved, have been manually controlled by operators. In general, providing these smaller vehicles with sophisticated, automated snow-ice control systems has been considered to be economically impractical. Such impracticality has been further evidenced by the restrictions posed by the more pronounced variations in cab layouts among the trucks mounts provided by various truck manufacturers. However, economic and environmental considerations now are changing the above-noted conventions for snow-ice control on secondary roadways. Significant economies are envisioned with accurate salt deposition and brining pre-treatment procedures. Notwithstanding the slower speeds involved, automated controls will be necessary to achieve such anticipated economies. However, a simplification of the installation of the automated systems is called for and when realized will have application not only to the smaller trucks but also to systems employed for treating primary highways.